Control system



Aug. 17, 1943. J. A. DEUBEL ET AL 2,326,767

CONTROL SYSTEM Filed July 17, 1940 INVENTORS' i j V W W ATTORNEY. I

Patented Aug. 17, 1943 T; ort l csf CONTROL SYSTEM I 7 Justin A. Deubel, Milwaukee, and Wayland 'R.

' Miller, Whitefish Bay, Wis., assignors to Perfex Corporation, Milwaukee, Wis., a corporation; of

Wisconsin Application July 17, 1940, Serial No. 345,914

' 12'Claims. This invention relates in general to automatic controls and more particularly to automatic control systems for stoker fired Warm air heating systems.

It has become common in the art to make provision for operating the fan or air circulating means of warm air heating systems during both summer and winter; During the heatingseason the fan is usually controlled so as to operate when the burner or stoker for the furnace is in operation. Usually the fan is controlled. by a thermostat responsive to the temperature in the bonnet of the heater so as to prevent opera tion of the fan whenever the delivery temperature of the air would be too low for comfort. In the summer, control of the fan isby a summer-winter switching mechanism transferred to a manual switch located at a suitable point so that the occupants may operate the fan at .will.

In the case of stoker fired systems, the stoker,

is usually provided witha timer or other fire maintaining device which operates the. Stoker at intervals independently of the thermostat for preventing the fire fromv going out in mild weather. In such systems, heretofore, arather complicated wiring arrangement utilizing a plurality ofrelays has been required in order to maintain the stoker control circuits separate from the fan control circuits, this being necessary in order to prevent the stoker timer from exerting a controllinginfluence on the fan..

It is an object of the present'inven'tion to provide a simplified control arrangement for con.- trolling systems of the type above mentioned. More specifically, an object of'this invention is the provision of a control system utilizing a control circuit controlled. either directly or.indirectlyrby a thermostat and a stoker timeror fire maintaining means, which control circuit. in

winter controls the stokervand circulating means and which in summer controls only the circu- .tion, the in 7 stoke r installations this control sequence is quite satisfactory and this control sequence being preferable' is utilized where possible. I stallations, however, this type of control "sequence is not entirely satisfactory; as stopping of the fan prevents all circulation of air through the system; Due to the factthat the fire. continues to burn at a fairly rapid rate for a period of time after the stoker is placed outof operarna'ce becomes overheatedzwith possible damage thereto; In systems having this characteristic, it, is necessary to. arrange the fan control so that the fan may operate as long as the furnace temperature is relatively high. Thus two different types of control systems having distinct sequences of operation have been required in order to'provide proper control for all types of systems. i

In providing vcontrols for systems of this type,

single primary control which consists of thenecessary relay, trans and other necessary it is desirable to provide a former, timing mechanism 7 instrumentalities, all located in a singleheusing. Due to; thef-act that two different wiring arrangements are: necessary for provi ding tl ie two sequences ofope ation, and as the wiring is located in the primary control unit, it has heretofore been necessary to carry in stock two types of primary control units, one type being a wired for the first mentioned sequence of operation and the other type'being' wired for the second sequence of operation. Thisgofjcourse,

increases thenumber of primary control'units carried in stock. In addition, Where installations 'z' are made with one type of the other type of control should have been used,

it is necessary for the service man to replace the control orto dismantle itin order to change the wiring.

lating means, a changeover means being prothe stoker is placed out of operation by the ther-i This stops the supply of heat :to the mostat. v heated space at the time-that the thermostat is satisfied and thus avoids any overrun in'temperaturezdue to continued supply of 5 heat after the thermostat is satisfied. For many types of simply shifting a selector sition to another.

It is a further .object ofthe present invention w1ring arrangement wherein theisequence of operation-of the system be chang'ed by member from one po- Anoth r object of this invention; is the provision of a summer-winter control unit having a I selector member as described aboveandr which includes a summer-winter changeover means which in its summer position places the thermoin-control 'ofthe fanirrespective of the position ofthe' selector member.

Other objects of various :1

stat control circuit the present invention" lie-in combinations, ,.subcombinations,. j and structures. of control equipment; which will be In some inprimary control where to provide a control system utilizing a novel 1 also actuates a cam 2 come apparent from the following description and the appended claims.

For a full disclosure of this invention reference is made to the following detailed description and to the accompanying drawing in which Fig. 1 illustrates diagrammatically a stoker fired warm air furnace having the control of the present invention applied thereto Fig. 2 is a wiring diagram of one form of the invention and which illustrates diagrammatically the various control devices, and in which Fig. 3 illustrates amodification. a r 1 Referring to Fig. 1, reference character I indicates a warm air furnace of usual construction,

this furnace being provided with a stoker 2 hav-,

ing a motor 3 and also being provided with a fan 4 which forces air to circulate through the return and discharge ducts of the usual-warm airheating system. Installed in the bonnet of the furnace l is a primary control device, this grammatically the control device located within the control housing 5 of the primary control, and also shows thewiring diagram for the system. The bimetallic element 6 is fixedly supported at one end and at its other is attached to a shafts. By this arrangement the shaft-8 is rotated by the element 6 upon change in-bonnet temperature. -The shaft 8 in the present embodiment of the invention carries a cam-fi which cooperates with a'switch formed of contact blades It and H to form 'a limit switch controlling the operation of the stoker motor. The cam 9 is provided with a raised portion'and a recessed portion as shown. This cam i mounted on the shaft 3 so as to maintain the switch blades H! and closed as 7 temperature is below'a predetermined high value. As the bonnet temperature rises the thermostatic element 5 will rotate shaft 8 and-cam -9 --in a clockwise direction. When the bonnet temperature rises to fthe'predet'ermined maximum value the'switch blade [I engages the recessed portion of thecame, thereby causing theswitch blades 19 and H to disengage. The shaft 8 M- which cooperates" with switch arms l5 and Hi to form afan switch for controlling the fan motor. The c am H is likewise provided with a'recessed' portion and a raised portion. When the bonnet temperature is below a predetermined minimum value the switch blade I5 engages the recessed portion of cam 54 and'thus disengages the switch arm 15. When the bonnet temperature" rises to a value at which fan operation may occur without discomfort to the occupants of the building, the raised portion of the cam for urging it"into engagement arm [5.

1 The thermostat shaft 8 also actuates a cam 18; which cam cooperates with a switch blade with the switch 19 adapted toselectively engage contacts 20 and- I 2|. The cam I3 is provided with a raised por- 'tion 22. Whenthe shaft 8 i rotated sufficiently to cause this raised portion 22- to engage the .switch blade |9,=this blade is urged into'engagement .with I the contact- 23. However, when the long as thefurnace or' bonn'et' 14 engages switch arm raised portion 22 of cam 18 is not in engagement with the switch blade i9, this switch blade engages the contact 2i as'shown. The arrangement just described provides a circuit change- 5 over switch, the purpose of which will become apparent as this description proceeds;

The thermostat shaft. S-alsoactuates a cam 25 [which cooperates with Switch blades 26 and 21 to form a timer control switch. The cam .10 2?) is provided with a recessed portion 28 and is arranged on the shaft 8 so that this recessed portion 22 engages switch blade 25 at approxi- --,lll2,t 1y.,the same time that the raised portion ,EZoficamiii engages switch blade it. The ther- 15 rirostat shaft; t is provided with a shaft which permits this shaft to be manually rotated against theyielding action of the thermostatic element -B. A latch device is provided for retaining the shaft; 8; in summer position, This latch member 20 may consist of a disc 3| attached to the shaft apin-33. By this-arrangementthe shaft 8 may -bemanually forced' in a clockwise direction-to a point at which the portions 22 and 28 of cams 25 :IB-and 2i engage their respective switch blades ;.or followers. The shaft fi may then be positioned inWardly-so-that the-slot:32 ofdisc 31 engages the --pin'33,:this serving to hold the shaft' 8 in summer position.

transformer, theprimary tdcf Which.is con nected-todine wires 31 and38. u'Ihis transformer 'includes .a secondarycoilitdwhich is adapted to energize the relaygenera'lly. indicated as it. The .relayati) maybe ofany desired construction and is. shown.-diagrammatically. as. com-prising .a pull- -in.coill-.fli .whichactuates through .a suitable armature 1a switch armffl cooperatingwith a contact 43. -.When.the.pul1-in. coilidi is energized, the. relay armature causes the switch arm..42 to '.be brought into-engagement with contact 43. .However, upon -de-energization .of coil M the switch armrfi'. .becomes. disengaged from. contact .43 due tothe action of'gravityor springsnot tfiishown. e i

-The.r.elay..4fi is' controlled by means of the room thermostat 'l,.a.manual.summer switch and a .stokeretimerifi. The-manualswitch 45 may be of anydesired-type:and is illustrated as comprising airnovableiswitch arm dl'adaptedto engage a contact .43.. :If.desired,;the switch 45 may be omitted; vthe control circuit .being 'manually -opened or closed in. summer by operating the .usual adjustment dial orrlever of .the roomther- .mostat; Thethermostat I likewise may be of .any..-suitable 'type and is. diagrammatically illus- -trated as. comprising a bimetallic. element 49 co- ,operating-with .a contactziii. 'fl hestoker timer,

1 or fire maintaining means, may. comprise .a small synchronous motor15 I :which. is. connected across -1ine .wires 3;! -and 33 by .wires 52,133 and 354 This motor 5.5. operates .acam :55 which cooperates .with .a .switch .arm 55 adapted to engage a icontact. 5l.' The cam 55 .is provided with recessed (35 portions which when engaging switch arm 55 permit this switch .arm to engage-contact 51. -Thus.rotationsotcam-di-by the motor- 5! causes .switch arm Siitoengage contact 51 atpredeterz-minedintervals. I

4'5 tproyide a.cen,tral control.unit or primarycontrol.

-8,' this diso-3 i-havinga slot-32 adapted toengage v The .various cam .operatedsswitches actuated ually control the fan at'will. Referring now to the wiring arrangement, the

secondary 39 of the transformer is connected by wire 60 to the element 49 of room thermostat 1. The contact 59 of this room thermostat is connected by wires Hand 52 to the pull-in coil 4| of relay 40. The other end of thiscoil is connected by wire 63 to the secondary 39. Upon fall in space temperature to the predetermined value, the element 49 engages contact 56 which causes energization of relay pull-in coll 4| by the circuit above traced. The summer switch 45 is connected into this circuit in parallel relationship with the thermostat 'I as' shown. Thus when this switch is closed the pull-in coil 4| is energized independently of the room thermostat l. The'switch arm 56 of the stoker timer is connectedto wire 60 by wire 64 and the contact 5'! is connected to the switch arm 26 of thetimer control switch by wire 95. The switch arm 21 of this switch is connected by wire 66 to the wire 6|. Thus when the timer control switch 26-27 is closed the stoker timer switch 56-51 periodically shunts'the room thermostat 1 for energiz ing the relay 49 independently of thermostat I. The switch arm 42 of the relay 4E isconnected by wire 61 to a jumper terminal 68 which is in turn connected by wires 69 and-"l to switch blade IQ of the limit switch and to contact 20 of the circuit changeover switch. A second jumper terminal TI is connected by wire 72 to the switch blade 55 of the fan switch andfa third jumper terminal '13 is connected by wire 14 to the switch arm I9 of the circuit changeover switch. A jumper T is provided and this jumper is adapted to be connected between either jumper terminals'BS and Has shownin full lines, or between jumper terminals H and 13 "as shown in dotted lines.

Operation For normal winter operation theshaft 8 is released from the restraining action of the latch 32-33 and is thus rotated by the thermostatic element 6 in response to changesinbo-nnet temperature. Also for normal winter operation, the summer switch 45 is in open position as shown. With the parts in the positions shown, the bonnet temperature is relatively low as indicated by the limit switch !BH being Closed and the fan switch [5-16 being open. It Will be noted that the cams l8 and 25 are so designed that switch arm l9 engagescontact Ziand the switch 26-21 remains closed unless shaft 3 rotates to an extreme clockwise position. In other words, the

rotation of the shaft 8 corresponding to maximum bonnet temperature is insufiicient to. cause cams I8 and 25 to actuate theirrespective switches from the positions shown. vAssumingnow that the room temperature falls' to a value requiring heat, the switch arm ,ofcthe thermostat 1' .will engage contact 59. This "willcomplete an energizing circuit forthe coil-ll of relay '48, thereby causing the relay switch arm 42350 engage 'contact 43. This will complete a circuit from line wire'3'l through contact 43, switch armfl, wires 67 and 69, switch blades l8 and II and wire 16 to" the stoker or fuel motor 3, thereby placing the stoker into operation. Due to theffan switch l5'|6 being open at thistime, the fan will remain at'rest. 'The operation of the-stoker will ingof the furnace might occur due tostoppingof the fanat thesame time that the stoker is placed" --out of operation. .In orderto provide propefr' V such characteristics the jumper is is shifted from its nurime' posi- :tion to its dotted line position. jWith this position of the jumper 'lfig theiuel motor 3, will con-' "tinueyto be energized in the. same t nanner as it shaft 8 clockwise.-

heat only occasionally.

.the fan without operating-thestoker.

For this position of 'gization of .However, the stoker motor 3 rises to a predetermined value the cam" M will cause engagement of'switch blades l5 and I6. I

This will complete a ci'rcuitfrom switch blade 42,'Wire 67, jumper 75, wire 12, and wire 11 t0 the fan motor, thereby placing the-fan into operation. In the event that the bonnet temperature rises to themaximum predetermined value, the recessed portion of the cam Swill engagethe switch blade H'for permitting this'switchblade to disengage the switch blade '90. thereby-opening'the circuit to the motor 3. 'This'williplace the stoker out of operation until the bonnet temperature falls to a value at which'thelimit switch Ill-l I again closes; It should be noted that the fan switch I 5l6 remains closed so that the fan continuesto operate even-thoughthe stoker is out of operation. Vfhen the room thermostat 49 will disengage r the circuit'for'coil H and therefore contacts as and 5B are open; the switch iii-+5101? the stoker timer closing periodically serves to energize the relay licfor brief in- .tervals. This serves to keep thefire aliveduringmild weather when the room thermostat calls for is desirable to operate For summer -operation,-the knob 38 is'rotated clockwise and pushed in so that the slot 32 engages pin 33. the shaft 3 the limit switch Iii-l I- will be open; he fan switchii-JB, will be closed, the switcharm [9 will engage-contact During the summer it '20, and the timer control switch'26+2'1 will be' open. During the summerv the room temperature will be above the control point of the room ther mostat 7 and consequently the element 49" there of Willfbe at all times disengaged from contact 50. When it is desired to operate the fan, the summer switch 45 is manually closedlwhich energizes the relayv 4o. Engagement of the switch arm "42 with the contact 53' will now causeenerthe fan motor due to the fact that the fan' switch 15-16 is now in closed position.

gized due to the fact that the shaft 8 is now positioned for opening the limit switch contacts I l3! I. -When the summer switch 55 is opened the relay 4% will -.become de-energizedfor stop ping the fan. It should be noted that during the summer the stoker timer is prevented from energizing 'the. relay coil il. bythe timer switch .,In some cases it is notrieasible to c'ontrlol the fan by the relayiduring-normal winter operation.

This is true in installations where an overheatcontrol for systems having was when the'jumperwas 'in' theffi'ill'line' posi 3 I in a short period of time cause'the'bonnet tern-" Yr perature to begin rising; thereby rotating the When the bonnet-temperature which prevents over-shooting ofthe room temperature; During the time when the 'room thermostat is satisfied;

will not. be 'enerby said summer-winter changeover means in its summer position for preventing said fire, maintaining means from influencing said relay.

' 2. In a control system for a space conditioning system including heating means having a stoker and mechanical circulating means for circulating heat exchange medium from said heating means to said space, the combination of, a relay having first and second positions and connected to said stoker and circulating means in a manner tending to place both into operation when the relay is in its first position and to place both out'of operation when the relay is in its second position, a control circuit for said relay including a thermostat for. causing said relay to assume its first position upon demand for heat in thespace and for causing itto assume its seccndposition when the demand for heat is satisfied, a heater thermostat influenced by the temperature of the heating means for preventing operation of the.

circulating means when the temperature ofthe heating means is low. While permitting operation ingheat exchange medium from said heating of the circulating meansunder the controLof the relay when said temperature is high, fire maintaining means including a switch connected: to said relay for'causing it at times to assume its first position independently-of said thermostat for'thereby maintaining the fire alive, sum mer-winter changeover means operative: in v its summer position to prevent operation of'said stoker by said relay and to render saidheater thermostat inefiective to prevent operation'of the circulating meansto thereby place the relay control circuit in control of said circulating means, and means Zcontrolled by said summerwinter changeover meansflin its summerposition for preventing causing actuation of said-relay. i

3. In a control system system including'heating means having. a stoker and mechanical circulating means for. circulating from saidheating means combination of, a thermostat. electric control circuit including a thermostat for placing said'stoker into operationupon 'de.-"- mand for heat in said space "and for normally stoker-yout of. operation whenthe heat is satisfied,:said electric control I heat exchange medium to said space, the

placing the demand for circuit also controlling saidcirculating means for causing it to operate at times when the striker is:

in operation, a heater thermostatin'fiuenced by the temperature of the heating means including first and second switches and thermostatic actusaidfire maintaining means from for a space conditioning ating means therefor for actuating saidswitches o,

in, sequence uponrise in heater temperature, said first switch being connected 'to said circulating means and being tion upon rise'intemperature of the heating means to a first value and said second switch being connected to said Stoker; and ibeing'shifted to on position upon rise insaid temperature to a predetermined maximum value, fire maintaining means including a'switch connected into said control circuit for operating said stoker independently of said thermostat to. thereby main shifted to running posi 'tain the fire alive, a manual operatorassociated.

with said heater thermostat and movable to a summer position wherein the first switch is maintained in running position and wherein the second switch is maintained in on, position, and

means operated by said manual movement to said summer position for preventing saidfiremaintaining means from influencing said control circuit. I V r V 4. In a control system for a space conditioning {and mechanical ing heat exchange medium from said heating system including' heating means having a stoker andmech'anical circulating means for circulatmeanstosaid space-the combinationof, a relay having first and secondpositions and connected, to said stoker and circulating means in a mannertending to place both into operation when the re,- lay is inits first position and to place both out of-operationwhen the relay is in its second position, acontrol circuit for said relay including a thermostat for causingsaid relay to assume its first position upon demand for heat in the space and for causing it to assume its second position whenithe'demand forheat is satisfied, a summer switch connected in said control circuit for causingisaid relay to assume its first position, fire,

maintaining means including a switching mechanism connected to the controlcircuit in a manner causing said relay to assume its first position at times independently of said thermostat formaintaining the fire alive, a heater thermostat influenced by the temperature-of the heating means includin first and second switches and thermostatic actuating means thereforfor actuating said switches in sequence upon rise in temperature andbeing. shifted to running position upon rise in temperature of the heating means 'to afirst value and said second switch being connected to said stokerandbeing shifted -to;off position upon rise in said temperature to a predetermined maximum value, a manual operator associated with said heater thermostat and movable to a summer a position wherein the-first switch is maintained in runningiposition and wherein the second switch is maintained in ofi position, and means including switchingmeans operated by said manual operator upon-movement to summerposition for preventing said fire maintaining means from infiuencing said control circuit. 7 t

system for a space conditioning heating meanshaving a stoker;

In a control system including circulating means for circulat means :to said space,-the. combination of, a relay having first and second positions and connected to said Stoker and circulating meansin'a man ner tending to place both into operation when the relay is inits first position and toplace both out of pperation'whenthe relay is in its second position, a control circuit for said relay includinga thermostat for causing said relay to assume its first position upondemand for heat in the space} and for causing it to assume itssecond po sition when the demand for heat is satisfied, a manual switch connected into said control circuit in series relationship with said thermostat 7 for providing summer control of the circulating means, fire maintaining means including switching mechanism connected to the relay control circuit in parallel relationship with thethermostat at times .independentlyof the thermostat for thereby maintaining the fire alive, a heater ,thermostat influenced by the temperature of the heating means including first and second switches and thermostatic actuating means therefor for i actuating said switches in sequence upon rise in operator upon temperature of the heating means, said first switchbeing connected to said circulating means and being'shifted to running position upon rise in said temperature to a first value andsaid sec- 0nd switch'being connected to said Stoker and shifted to off position upon rise in said tembeing v of the heatingmeans, said firstf switch beingconnected to said circulating: means 7 for causing saidrelay to assume its first position its second position when the demand for heat is satisfied, circuit means including a heater thermostat arranged to place the circulating means in operation when the temperature of the heating means rises to a predetermined value, fire maintaining means for controlling the relay independently of the space thermostat to cause said relay to assume its first position at times inde pendently of said thermostat, and summer-winter changeover means arranged, when in its winter position to render the relay capable of operating the stoker when the relay assumes its first position, said changeover means when in its summer position rendering the relay capable of causing operation of the circulating means when the relay assumes its first position preventing the relay from operating the sto-lser; and preventing the fire maintaining means from controlling the relay.

11. In a control system for a space conditioning system including heating means having astoker and mechanical circulating means for circulat-. ing heat exchange medium from g the heating means to the space, the combination of, a relay having first and second positions, circuit means connecting the relay and stoker for causing operation of the sto-ker when the relay is in its first position, a control circuit for the relay including a space thermostat for causing the relay to assume its first position upon demand for heat in the space and to assume its second position when the demand for heat is satisfied, fire maintainin means for controlling the stoker to cause ope'ration of the stoker at time independently of the space thermostat to thereby maintain the fire operation whenthe temperature of the heating means rises to a predetermined Value, and summer-winter changeover means arranged when in its winter position to place the stoker under the control of said relay, said changeover means when in its summer position rendering the relay capable, of causing operation of the circulating means when the relay assumes its first position;

preventing the relay from operating the stoker; andpreventing the fire maintaining means from 'causing'operation of thecirculatingmeans'. I

12. In a control system for a space conditioning system including heating mean having combustion means and mechanical circulating means for circulating heat exchange medium from the heat-- 7,

- ing means to the space, the combination of, a'

- relay having first and second positions, a control circuit for the relay including a space thermostat for causing the relay toassume its first position. upon'demand for heat and toassume its second position when'the demand for heat is satisfied, a heater thermostat including a switch which opens when the temperature of the heating means is relatively low and which closes when said temperature rises toa higher value, circuit means for erative in one position 'toplace th relay and heater thermostat in conjoint control of the cir- V culating' meansand operativein another position to place the heater thermostat incontrol of the circulating means independently of the relay, and summer-winter changeover means arranged I when: in its winter position to place therelay incontrol of the combustion means, said change I position preventing the relay from placing the combustion means over means when initssummer in operation and rendering the relay in its first position capable of operating thecirculating meansirrespective of said selective means," 1

JUSTIN A. I DEUBEL. 7 WAYLAND R," I L R,

alive, circuit means including a heater thermostat arranged to place the circulating means in, 

